On Tue, May 21, 2013 at 03:01:08PM -0700, Alexander Duyck wrote: > On 05/21/2013 02:49 PM, Michael S. Tsirkin wrote: > > On Tue, May 21, 2013 at 05:30:32PM -0400, Don Dutile wrote: > >> On 05/14/2013 05:39 PM, Alexander Duyck wrote: > >>> On 05/14/2013 12:59 PM, Yinghai Lu wrote: > >>>> On Tue, May 14, 2013 at 12:45 PM, Alexander Duyck > >>>> <alexander.h.duyck@xxxxxxxxx> wrote: > >>>>> On 05/14/2013 11:44 AM, Yinghai Lu wrote: > >>>>>> On Tue, May 14, 2013 at 9:00 AM, Alexander Duyck > >>>>>> <alexander.h.duyck@xxxxxxxxx> wrote: > >>>>>>> I'm sorry, but what is the point of this patch? With device assignment > >>>>>>> it is always possible to have VFs loaded and the PF driver unloaded > >>>>>>> since you cannot remove the VFs if they are assigned to a VM. > >>>>>> unload PF driver will not call pci_disable_sriov? > >>>>> You cannot call pci_disable_sriov because you will panic all of the > >>>>> guests that have devices assigned. > >>>> ixgbe_remove did call pci_disable_sriov... > >>>> > >>>> for guest panic, that is another problem. > >>>> just like you pci passthrough with real pci device and hotremove the > >>>> card in host. > >>>> > >>>> ... > >>> > >>> I suggest you take another look. In ixgbe_disable_sriov, which is the > >>> function that is called we do a check for assigned VFs. If they are > >>> assigned then we do not call pci_disable_sriov. > >>> > >>>> > >>>>> So how does your patch actually fix this problem? It seems like it is > >>>>> just avoiding it. > >>>> yes, until the first one is done. > >>> > >>> Avoiding the issue doesn't fix the underlying problem and instead you > >>> are likely just introducing more bugs as a result. > >>> > >>>>> From what I can tell your problem is originating in pci_call_probe. I > >>>>> believe it is calling work_on_cpu and that doesn't seem correct since > >>>>> the work should be taking place on a CPU already local to the PF. You > >>>>> might want to look there to see why you are trying to schedule work on a > >>>>> CPU which should be perfectly fine for you to already be doing your work on. > >>>> it always try to go with local cpu with same pxm. > >>> > >>> The problem is we really shouldn't be calling work_for_cpu in this case > >>> since we are already on the correct CPU. What probably should be > >>> happening is that pci_call_probe should be doing a check to see if the > >>> current CPU is already contained within the device node map and if so > >>> just call local_pci_probe directly. That way you can avoid deadlocking > >>> the system by trying to flush the CPU queue of the CPU you are currently on. > >>> > >> That's the patch that Michael Tsirkin posted for a fix, > >> but it was noted that if you have the case where the _same_ driver is used for vf & pf, > >> other deadlocks may occur. > >> It would work in the case of ixgbe/ixgbevf, but not for something like > >> the Mellanox pf/vf driver (which is the same). > >> > > > > I think our conclusion was this is a false positive for Mellanox. > > If not, we need to understand what the deadlock is better. > > > > As I understand the issue, the problem is not a deadlock for Mellanox > (At least with either your patch or mine applied), the issue is that the > PF is not ready to handle VFs when pci_enable_sriov is called due to > some firmware issues. > > Thanks, > > Alex I haven't seen Mellanox guys say anything like this on the list. Pointers? All I saw is some lockdep warnings and Tejun says they are bogus ... -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
